Most old school D&D players realize that it is fairly easy to use an adventure written for one version of TSR D&D with the rules for a different version of TSR D&D. While each version (OD&D, Holmes D&D, 1e, B/X, BECMI, 2e, and RC) are different enough to be separate games, they have some much in common that it often takes little effort to use an adventure or setting designed for one version with another version. In most cases, many experienced GMs can convert adventures on the fly as they run them.

A lot of people used to mix rules in play as well. Many people playing AD&D were actually using the less complex systems from B/X D&D with the classes, spells, monsters, and magic items from AD&D. Others just added what they liked from second edition AD&D to their first edition AD&D games. And so forth.

This got me thinking, what would a "best of" set of rules taken from all of the versions of D&D TSR published look like. Naturally it would look different to different people because everyone interested in TSR D&D likely has different ideas of what the best rules in TSR D&D were. While I haven't given this the hours of thought I would need to if I were going to actually write such a set of rules, I can immediately list some of the important rules pieces that were be in my personal "Best of TSR" edition of D&D.

* I'd use the basic game systems from B/X D&D as they are clear and fairly simple.

* Race and Class would come from AD&D, mostly from 1e. The Bard however, would come from 2e. I'll probably also use the specialist priest material from 2e.

* Spells would come mainly from 1e. 1e has a somewhat larger selection than OD&D or B/X, but not the seemingly endless list that 2e plus supplements had.

* Monsters and Treasure would mainly come from 1e. Again, 2e just as too many.

* I'd take the domain and mass combat rules from BECMI/RC.

If you were designing a "best of TSR" set of D&D rules, what would you include?

This is something I think about and hem-n-haw over a lot. Sometimes I love straight B/X, but sometimes I find the simplicity of Holmes Basic (with abilities that provide no bonus) to be the perfect ideal. I recently had a chance to play in someone's (slightly modified) OD&D campaign and found the simplicity of unified D6 damage and hit dice to be just fine and dandy...but sometimes I want to use my various dice to model different effects.

In other words: even for a single individual (me) what I want from my D&D game changes a lot depending on setting, scenario, nostalgia, and whim. So many neat ways to accomplish so many different things.

For me, it's been a mix of a lot of Philotomy's rule from OD&D (combat sequence, scroll creation), blog/forum contributions from the late aughts (Delta's Target20, OD&D Boards counterspelling, others), my own creations and adaptations from Holmes and B/X layered on top of (or replacing) AD&D 1e.

I am not sure why OSR should be restrictive to TSR content.I play D&D using any of the rules from any of the editions as my "house rules". (exception: I use material from the 4th edition adventures but none of THOSE rules, for they are incompatible) I was introduced to 1st edition AD&D then got a Basic Mentzer Red Box and Expert. Then bought 2nd AD&D players handbook. Played 3.5 and Pathfinder for years. And now LOVE the new 5th edition Monster Manual and the "Bounded Accuracy" Concept. Dungeons & Dragons is a living, evolving game and I see no reason to restrict your house rules to a given time frame. My home game continues to evolve as I find things that work better.I think that making the game your own is as old school as anyone can get.